38 lines
1.2 KiB
C
38 lines
1.2 KiB
C
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#include <c3d/maths.h>
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void Mtx_PerspStereoTilt(C3D_Mtx* mtx, float fovx, float invaspect, float near, float far, float iod, float screen)
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{
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// Notes:
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// Once again, we are passed "fovy" and the "aspect ratio"; however the 3DS screens are sideways,
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// and the formula had to be tweaked. With stereo, left/right separation becomes top/bottom separation.
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// The detailed mathematical explanation is in mtx_persptilt.c.
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float fovx_tan = tanf(fovx/2);
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float fovx_tan_invaspect = fovx_tan*invaspect;
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float shift = iod / (2*screen); // 'near' not in the numerator because it cancels out in mp.r[1].z
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C3D_Mtx mp;
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Mtx_Zeros(&mp);
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// Build asymmetric perspective projection matrix
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mp.r[0].x = 1.0f / fovx_tan;
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mp.r[1].y = 1.0f / fovx_tan_invaspect;
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mp.r[1].z = shift / fovx_tan_invaspect;
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mp.r[2].z = (near + far) / (near - far);
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mp.r[2].w = (2 * near * far) / (near - far);
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mp.r[3].z = -1.0f;
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// Fix depth range to [-1, 0]
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C3D_Mtx mp2;
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Mtx_Identity(&mp2);
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mp2.r[2].z = 0.5;
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mp2.r[2].w = -0.5;
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Mtx_Multiply(mtx, &mp2, &mp);
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// Translate to screen plane
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Mtx_Translate(mtx, 0, iod/2, 0);
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// Rotate the matrix one quarter of a turn CCW in order to fix the 3DS screens' orientation
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Mtx_RotateZ(mtx, M_TAU/4, true);
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}
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